/Engine/Plugins/Editor/GeometryMode/Source/GeometryMode/Public/EditorGeometry.h
Set the pivot position based on the 'highest' selected object (vertex/edge/poly) in the given selection array
The index of the array entry used for setting the pivot. Returns INDEX_NONE if pivot not set
int32 SetPivotFromSelectionArray ( [TArray](API\Runtime\Core\Containers\TArray)< struct [FGeomSelection](API\Runtime\Engine\Engine\FGeomSelection) > & SelectionArray )